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Diffstat (limited to 'python/macholib/macholib/MachO.py')
| -rw-r--r-- | python/macholib/macholib/MachO.py | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/python/macholib/macholib/MachO.py b/python/macholib/macholib/MachO.py new file mode 100644 index 000000000..f83ddb711 --- /dev/null +++ b/python/macholib/macholib/MachO.py @@ -0,0 +1,398 @@ +""" +Utilities for reading and writing Mach-O headers +""" +from __future__ import print_function + +import sys +import struct + +from macholib.mach_o import * +from macholib.dyld import dyld_find, framework_info +from macholib.util import fileview +try: + from macholib.compat import bytes +except ImportError: + pass + +try: + unicode +except NameError: + unicode = str + +__all__ = ['MachO'] + +_RELOCATABLE = set(( + # relocatable commands that should be used for dependency walking + LC_LOAD_DYLIB, + LC_LOAD_WEAK_DYLIB, + LC_PREBOUND_DYLIB, + LC_REEXPORT_DYLIB, +)) + +_RELOCATABLE_NAMES = { + LC_LOAD_DYLIB: 'load_dylib', + LC_LOAD_WEAK_DYLIB: 'load_weak_dylib', + LC_PREBOUND_DYLIB: 'prebound_dylib', + LC_REEXPORT_DYLIB: 'reexport_dylib', +} + +def _shouldRelocateCommand(cmd): + """ + Should this command id be investigated for relocation? + """ + return cmd in _RELOCATABLE + +class MachO(object): + """ + Provides reading/writing the Mach-O header of a specific existing file + """ + # filename - the original filename of this mach-o + # sizediff - the current deviation from the initial mach-o size + # header - the mach-o header + # commands - a list of (load_command, somecommand, data) + # data is either a str, or a list of segment structures + # total_size - the current mach-o header size (including header) + # low_offset - essentially, the maximum mach-o header size + # id_cmd - the index of my id command, or None + + + def __init__(self, filename): + + # supports the ObjectGraph protocol + self.graphident = filename + self.filename = filename + + # initialized by load + self.fat = None + self.headers = [] + with open(filename, 'rb') as fp: + self.load(fp) + + def __repr__(self): + return "<MachO filename=%r>" % (self.filename,) + + def load(self, fh): + assert fh.tell() == 0 + header = struct.unpack('>I', fh.read(4))[0] + fh.seek(0) + if header == FAT_MAGIC: + self.load_fat(fh) + else: + fh.seek(0, 2) + size = fh.tell() + fh.seek(0) + self.load_header(fh, 0, size) + + def load_fat(self, fh): + self.fat = fat_header.from_fileobj(fh) + archs = [fat_arch.from_fileobj(fh) for i in range(self.fat.nfat_arch)] + for arch in archs: + self.load_header(fh, arch.offset, arch.size) + + def rewriteLoadCommands(self, *args, **kw): + changed = False + for header in self.headers: + if header.rewriteLoadCommands(*args, **kw): + changed = True + return changed + + def load_header(self, fh, offset, size): + fh.seek(offset) + header = struct.unpack('>I', fh.read(4))[0] + fh.seek(offset) + if header == MH_MAGIC: + magic, hdr, endian = MH_MAGIC, mach_header, '>' + elif header == MH_CIGAM: + magic, hdr, endian = MH_CIGAM, mach_header, '<' + elif header == MH_MAGIC_64: + magic, hdr, endian = MH_MAGIC_64, mach_header_64, '>' + elif header == MH_CIGAM_64: + magic, hdr, endian = MH_CIGAM_64, mach_header_64, '<' + else: + raise ValueError("Unknown Mach-O header: 0x%08x in %r" % ( + header, fh)) + hdr = MachOHeader(self, fh, offset, size, magic, hdr, endian) + self.headers.append(hdr) + + def write(self, f): + for header in self.headers: + header.write(f) + +class MachOHeader(object): + """ + Provides reading/writing the Mach-O header of a specific existing file + """ + # filename - the original filename of this mach-o + # sizediff - the current deviation from the initial mach-o size + # header - the mach-o header + # commands - a list of (load_command, somecommand, data) + # data is either a str, or a list of segment structures + # total_size - the current mach-o header size (including header) + # low_offset - essentially, the maximum mach-o header size + # id_cmd - the index of my id command, or None + + + def __init__(self, parent, fh, offset, size, magic, hdr, endian): + self.MH_MAGIC = magic + self.mach_header = hdr + + # These are all initialized by self.load() + self.parent = parent + self.offset = offset + self.size = size + + self.endian = endian + self.header = None + self.commands = None + self.id_cmd = None + self.sizediff = None + self.total_size = None + self.low_offset = None + self.filetype = None + self.headers = [] + + self.load(fh) + + def __repr__(self): + return "<%s filename=%r offset=%d size=%d endian=%r>" % ( + type(self).__name__, self.parent.filename, self.offset, self.size, + self.endian) + + def load(self, fh): + fh = fileview(fh, self.offset, self.size) + fh.seek(0) + + self.sizediff = 0 + kw = {'_endian_': self.endian} + header = self.mach_header.from_fileobj(fh, **kw) + self.header = header + #if header.magic != self.MH_MAGIC: + # raise ValueError("header has magic %08x, expecting %08x" % ( + # header.magic, self.MH_MAGIC)) + + cmd = self.commands = [] + + self.filetype = self.get_filetype_shortname(header.filetype) + + read_bytes = 0 + low_offset = sys.maxsize + for i in range(header.ncmds): + # read the load command + cmd_load = load_command.from_fileobj(fh, **kw) + + # read the specific command + klass = LC_REGISTRY.get(cmd_load.cmd, None) + if klass is None: + raise ValueError("Unknown load command: %d" % (cmd_load.cmd,)) + cmd_cmd = klass.from_fileobj(fh, **kw) + + if cmd_load.cmd == LC_ID_DYLIB: + # remember where this command was + if self.id_cmd is not None: + raise ValueError("This dylib already has an id") + self.id_cmd = i + + if cmd_load.cmd in (LC_SEGMENT, LC_SEGMENT_64): + # for segment commands, read the list of segments + segs = [] + # assert that the size makes sense + if cmd_load.cmd == LC_SEGMENT: + section_cls = section + else: # LC_SEGMENT_64 + section_cls = section_64 + + expected_size = ( + sizeof(klass) + sizeof(load_command) + + (sizeof(section_cls) * cmd_cmd.nsects) + ) + if cmd_load.cmdsize != expected_size: + raise ValueError("Segment size mismatch") + # this is a zero block or something + # so the beginning is wherever the fileoff of this command is + if cmd_cmd.nsects == 0: + if cmd_cmd.filesize != 0: + low_offset = min(low_offset, cmd_cmd.fileoff) + else: + # this one has multiple segments + for j in range(cmd_cmd.nsects): + # read the segment + seg = section_cls.from_fileobj(fh, **kw) + # if the segment has a size and is not zero filled + # then its beginning is the offset of this segment + not_zerofill = ((seg.flags & S_ZEROFILL) != S_ZEROFILL) + if seg.offset > 0 and seg.size > 0 and not_zerofill: + low_offset = min(low_offset, seg.offset) + if not_zerofill: + c = fh.tell() + fh.seek(seg.offset) + sd = fh.read(seg.size) + seg.add_section_data(sd) + fh.seek(c) + segs.append(seg) + # data is a list of segments + cmd_data = segs + + # XXX: Disabled for now because writing back doesn't work + #elif cmd_load.cmd == LC_CODE_SIGNATURE: + # c = fh.tell() + # fh.seek(cmd_cmd.dataoff) + # cmd_data = fh.read(cmd_cmd.datasize) + # fh.seek(c) + #elif cmd_load.cmd == LC_SYMTAB: + # c = fh.tell() + # fh.seek(cmd_cmd.stroff) + # cmd_data = fh.read(cmd_cmd.strsize) + # fh.seek(c) + + else: + # data is a raw str + data_size = ( + cmd_load.cmdsize - sizeof(klass) - sizeof(load_command) + ) + cmd_data = fh.read(data_size) + cmd.append((cmd_load, cmd_cmd, cmd_data)) + read_bytes += cmd_load.cmdsize + + # make sure the header made sense + if read_bytes != header.sizeofcmds: + raise ValueError("Read %d bytes, header reports %d bytes" % ( + read_bytes, header.sizeofcmds)) + self.total_size = sizeof(self.mach_header) + read_bytes + self.low_offset = low_offset + + # this header overwrites a segment, what the heck? + if self.total_size > low_offset: + raise ValueError("total_size > low_offset (%d > %d)" % ( + self.total_size, low_offset)) + + def walkRelocatables(self, shouldRelocateCommand=_shouldRelocateCommand): + """ + for all relocatable commands + yield (command_index, command_name, filename) + """ + for (idx, (lc, cmd, data)) in enumerate(self.commands): + if shouldRelocateCommand(lc.cmd): + name = _RELOCATABLE_NAMES[lc.cmd] + ofs = cmd.name - sizeof(lc.__class__) - sizeof(cmd.__class__) + yield idx, name, data[ofs:data.find(b'\x00', ofs)].decode( + sys.getfilesystemencoding()) + + def rewriteInstallNameCommand(self, loadcmd): + """Rewrite the load command of this dylib""" + if self.id_cmd is not None: + self.rewriteDataForCommand(self.id_cmd, loadcmd) + return True + return False + + def changedHeaderSizeBy(self, bytes): + self.sizediff += bytes + if (self.total_size + self.sizediff) > self.low_offset: + print("WARNING: Mach-O header in %r may be too large to relocate"%(self.parent.filename,)) + + def rewriteLoadCommands(self, changefunc): + """ + Rewrite the load commands based upon a change dictionary + """ + data = changefunc(self.parent.filename) + changed = False + if data is not None: + if self.rewriteInstallNameCommand( + data.encode(sys.getfilesystemencoding())): + changed = True + for idx, name, filename in self.walkRelocatables(): + data = changefunc(filename) + if data is not None: + if self.rewriteDataForCommand(idx, data.encode( + sys.getfilesystemencoding())): + changed = True + return changed + + def rewriteDataForCommand(self, idx, data): + lc, cmd, old_data = self.commands[idx] + hdrsize = sizeof(lc.__class__) + sizeof(cmd.__class__) + align = struct.calcsize('L') + data = data + (b'\x00' * (align - (len(data) % align))) + newsize = hdrsize + len(data) + self.commands[idx] = (lc, cmd, data) + self.changedHeaderSizeBy(newsize - lc.cmdsize) + lc.cmdsize, cmd.name = newsize, hdrsize + return True + + def synchronize_size(self): + if (self.total_size + self.sizediff) > self.low_offset: + raise ValueError("New Mach-O header is too large to relocate in %r"%(self.parent.filename,)) + self.header.sizeofcmds += self.sizediff + self.total_size = sizeof(self.mach_header) + self.header.sizeofcmds + self.sizediff = 0 + + def write(self, fileobj): + fileobj = fileview(fileobj, self.offset, self.size) + fileobj.seek(0) + + # serialize all the mach-o commands + self.synchronize_size() + + self.header.to_fileobj(fileobj) + for lc, cmd, data in self.commands: + lc.to_fileobj(fileobj) + cmd.to_fileobj(fileobj) + + if sys.version_info[0] == 2: + if isinstance(data, unicode): + fileobj.write(data.encode(sys.getfilesystemencoding())) + + elif isinstance(data, (bytes, str)): + fileobj.write(data) + else: + # segments.. + for obj in data: + obj.to_fileobj(fileobj) + else: + if isinstance(data, str): + fileobj.write(data.encode(sys.getfilesystemencoding())) + + elif isinstance(data, bytes): + fileobj.write(data) + + else: + # segments.. + for obj in data: + obj.to_fileobj(fileobj) + + # zero out the unused space, doubt this is strictly necessary + # and is generally probably already the case + fileobj.write(b'\x00' * (self.low_offset - fileobj.tell())) + + def getSymbolTableCommand(self): + for lc, cmd, data in self.commands: + if lc.cmd == LC_SYMTAB: + return cmd + return None + + def getDynamicSymbolTableCommand(self): + for lc, cmd, data in self.commands: + if lc.cmd == LC_DYSYMTAB: + return cmd + return None + + def get_filetype_shortname(self, filetype): + if filetype in MH_FILETYPE_SHORTNAMES: + return MH_FILETYPE_SHORTNAMES[filetype] + else: + return 'unknown' + +def main(fn): + m = MachO(fn) + seen = set() + for header in m.headers: + for idx, name, other in header.walkRelocatables(): + if other not in seen: + seen.add(other) + print('\t' + name + ": " + other) + +if __name__ == '__main__': + import sys + files = sys.argv[1:] or ['/bin/ls'] + for fn in files: + print(fn) + main(fn) |